This invention relates to conveyor-type load-moving systems having a load-moving belt or band which extends between respective wind-up rolls and is wound on one or other of the rolls to move the load in one or other direction.
A load-moving system of the above type may be used for example on trucks or trailers for loading or unloading the vehicle through the back end thereof by means of a powered conveyor belt or band extending along the bed of the vehicle between front and rear wind-up rolls. Thus, the belt or band may be attached at its forward end to a front wind-up roll which is located internally of the truck or trailer adjacent its front wall and the rear end of the belt or band may be attached to a rear wind-up roll which may be located externally under the back end of the truck or trailer. When loading the vehicle, the belt or band is wound onto the front roll, by driving the front roll and, conversely, for unloading the truck or trailer, the belt or band is wound onto the back roll by driving this roll. The rear wind-up roll may, for example, be located in a casing slung beneath the back end of the truck or trailer.
A-conveyor-type load-moving system of the above type can also be used on a stationary body such as a loading dock. It is desirable in loading and unloading systems of the above type to provide some form of remote control for the drive mechanisms used to operate the respective wind-up rolls so that the loading and unloading can be controlled by an operator outside of the vehicle. It is further desirable to provide means within the control system to prevent the belt or band from being pulled off a respective wind-up roll or drum by overwinding the other roll or drum one means for preventing the belt or band from being pulled off the drums includes the use of a proximity switch sensing a metal tab or the like fixed to the belt at an appropriate point and shutting down the drive mechanism in response to the tab being sensed. This form of control means is useful for loading and unloading to and from a loading dock because it allows an operator to work through a push button control pendant at the end of an electrical cable. This form of control system, however, also has relatively delicate components and may not therefore be suitable for use in certain applications where, for example, bulk materials such as refuse are to be handled and where the belt or band may be subject to heavy duty use. Accordingly, the present invention provides an alternative form of control system for preventing the belt or band from being pulled off the wind up rolls or drums at the opposite ends of its travel.